Method of burnishing gears



March 16 1926. 1,576,806

\ B. H. BLQOD METHOD OF BURNISHING GEARS- Filed Nov. s,v 1922 2 Sheets-Sheet 1 a iyz/p w ATTORNEY March 16 1926?" B. H. BLOOD METHOD OF BURNISHING GEARS Filed Nov. 6, 1922 2 Sheets-Sheet 2 Patented Mar. 1a, was.

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Application ma s ear a, 1m. "serial in. mm. I

I State of Connecticut, have invented certain new and useful Improvements in Methods of Burnishing Gears, of which the following is a specification. I

This invention relates .to an improved,

10 form of gear burnishing device and man improved method of burnishing gears.

An object of the present invention 13 to provide a gear burnishing machine or de-" vice .adapted to facilitate and expedite the mounting of the gear tobe burnished-and to "enable a. gear to bequickly burnished, prefv erably by a plurality of burnishers.

Another 'object of theinvention is to provide a burnisher adapted to control the burnishing action so-that preferably points of the teeth on the gear being burnished and parts adjacent thereto will have more burnishing action applied to them than the remaining parts of the gear teeth.

Another object of the invention is to provide a burn-ishing machine or device mounting a plurality of burnishers in the form of gears, these burnishers" having ,teeth of slightly difierentcharacter in order to vary 3 adapted to control the burnishing\action upon diflerent parts oi the gearbeing'acted upon. a In practice, it. heretofore has been the custom to burnish gears by running them while in mesh with other gears'of corresponding pitch" until the surfaces of the gear being burnished are sufiiciently uniformly smoothed'for' roper action. Ihave strongly burnish the points of the teeth than the parts of the teeth adjacent and below lish this object and to definitely control the urnishing' action' by. slightly varying the characters of tooth: outlines on the burnishers.

In the succeeding paragraphs reference I willbe made to the basecircle, thepitch' their burnishingaction' upon the gear and found, however,-that it is desirable to more I the pitch circle. Iqam enabled to. accom-' m1 pitch is not, well or generallyknown' so. that a definition of-this term is necessary. TlllS term refers to the'base circle and indicates the .pitch 'on-that'oircle, that is, the

linear distance between adjacent corres 0ndlng inyolutes as measured on arcs 0 this base -c1rcle.'- Mathematically speaking, the

normal pitch corresponds to the circular pitch ofthe gear multiplied by the cosine of the pressure angle. In other terms, it I equal the circumference of the base. circle divided by the number of teeth in the gear.

It is therefore .a principal-objeet of the present invention to so form the tooth curves i of the burnishers that they will concentrate their burni'sliing action uponthe points of the gear teeth and parts adjacent thereto; I accomplish this object by varying slightly 'the normal pitch. of the involutes on the burnishers 'as compared with the normal pitch of the involutes on the gear.

Some of the advantages of my improved method of burnishing may be obtained by burnishing the tooth curves adjacent the base of the involutes instead of at and adjacent their outer points.

. In order to concentrate action adjacent the lower fla-nkportions, I

an; burnishing use a burnisher having teeth whose normal pitch is slightly increased instead of decreased as compared with the gear being burnished. This gives a form of tooth of apparently slightly less pressure angle and the points on the teeth of the burnisher are therefore forced'into strong contactwith the flanks of the gear being burnished. In this way, they contact with and concentrate their burnishing action upon these lower portions of the gear teeth;-

g In the drawings,'forms of burnishers '1 are disclosed which in their action concentrate the burnishing. of the-tooth curves upon their points, theirinrier flank portions, and

uniformly fupon the involute contour, thisbeing the preferred form of the invention.

These burnishers maybe used singly or in roups. as desired, It is to be understood,

owever, that certain conditions may arise wherein-it will be more desirable thatthe teeth of the gears bein burnished be more i 7 strongly burnished. a jacent their roots rather than at their points and I control thisburnishing. action by selecting bur.

nishera having taeth'jof sligh ly m dified invention consists in the features of normal pitch. To concentrate the burnishing action on the points of the teeth the normal pitch of the burnisher is slightly lessened and to more strongly burnish the flanks or portions within the pitch circle. the normal pitch of the burnisher is'slightly increased. V

In either case, I prefer to run the gears being burnished in contact with a plurality of burnishers, one or more of which may be of modified normal pitch. If a plurality of burnishers areused s1- multaneously, a method to be preferred, the base circles of the burnishers may be slightly varied between themselves. Ineach case the normal pitches of the tooth curves of the burnishers vary but slightly from the normal pitch of the gear being burnished. The variation in the normal pitch ofthe tooth curves on the burnishers does not.

affect the other characteristics of the teeth n the burnisher. The number of teeth on he burnishers therefore may be selected for convenience and these may be used for bur- .-iishing gears having any number of teeth of the same nominal size. I

With these and other objects in view, my

construction and operation set forth in the following specification and illustrated l'n the accompanying drawing.

In the drawing annexed hereto and forming a part of this specification, I have shown my invention in the form of a device adapted to be mounted on a milling machine. but it will be understood that the invention can be otherwise embodied and that the drawing is not to be construed as defining or limiting the scope of the invention, the claims appended to this specification being relied upon for that purpose.

In the drawing:

Figure 1 is a front elevation of a device for burnishin gears made in accordance with the present invention.

Fig. 2 is a side elevation ,of the same. Fig. 3 is a diagrammatic view showing the teeth of a gear and burnisher in intermeshing relation.

Fig. 4 is a view similar to Fig. 3, and Fig. 5 is an enlarged view of a gear being burnished by three burnishers having different normal pitches.

In the above mentioned drawing, I have shown but one embodiment of the invention which is now deemed preferable but it is to be understood that changes and modifications may be made within the scope of the appended claims without depart-mg from the spirit of the invent1on.

Briefly, my invention preferably comprises a device which for convenience may be mounted upon a milling machine of con ventional or ordinary form and consists gen-- erally of; first, a base adapted to be directly fastened to the tab e of the m g m ehm second, a pair of burnishers'in the form of gears rotatably mounted upon parallel axes in the said base; third, another burnisher of similar form which for convenience may be applied to the cutter spindle of the milling machine; and fourth. means to rotate one of the burnishers while the gear being burnished is in position to intcrmesh with all three burnishers. 7

Referring more in detail to the figures of the drawing, I show a milling machine 10 of conventional form having a vertically adjustable knee 11 on which is slidably mounted a saddle 12 which may be moved in a direction parallel to the axis of the cutter spindle 13 of the milling machine. On this saddle 12, or intermediate slide, is the usual reciprocatory table 14 which may be movable in a direction normal to that of the saddle or intermediate slide 12.

The milling machine 10 is provided with acone pulley 15 or other driving means for the spindle 13. and also with an overhanging arm 16 of usual construction to aid in supporting an arbor 17 mounted on and rotated by the spindle 13.

. A base 20 shown most clearly in Fig. 1 is fastened to the upper surface of the milling machine table 14 in any convenient way. Extending through this base member 20 are parallel spindles 21 preferably held fixedly therein by any convenient means. Rotatably mounted upon these parallel spindles 21 are burnishers 22 and 23 preferably of approximately equal size and numbers of teeth. These, as is usual in burnishing devices are hardened and are also preferably ground so that the tooth outlines thereon, which are usually of involute form, are correct to a high degree of precision.

Mounted on the arbor 17 of the milling machine 10 is a third burnisher 24 which may be directly fastened thereto so that it will rotate with the spindle and will be rotated by any convenient power means as by the pulley 15. By varying-the elevation it will rotate the gear A being burnished and the two lower burnishers 22 and 23. By forcing the adjustable knee 11 vertically upward any desired pressure may be exerted by the burnishers 22, 23 and 24 upon tlie tooth curves of the gear A. I preferably form the burnishers 22-, 2-3 and 24 of wider face than the gear A being burnished so that, if desired, the gear may be moved axially forward or backward to insure even wear on'the burnishers and more uniform burnishing action on the gear.

In order to accomplish an improved burnishlng action whichwil'l render the gear more quiet in operation than any other '5 I accomplish this by varying the tooth curves on the burnishers with relation to the gears being may have, or. at least one of them may have, a normal pitch slightly-less than the normal 'pitch of the gears being burnished. Preferably as there arethree burnishers simultaneously acting on the gear, I make one of these burnishers to correspond-exactly with the normal itch of the gear and the other two burnis ers of. different normal pitch, one of which may be slightly less than the normal pitch of the gear and the other slightly more, as shown in Fig. 5. If desired,.however, all three of the burnishers may be made of equal normal itch slightly less than the normal pitch of t e gear being burnished.

Referring to the diagrams in Figs. 3 and 4, a few of the teeth of the'gear A being burnished in action with the teeth of a burnisher are described. In ig.'3, the normal pitch of the burnisher 24 is identical with that of the gear A as indicated by the identical lengths of the lines a and i). In other words, the teeth of this burnisher are of the form of gear teeth adapted to inter-mesh with the gear in the usual manner. This figure shows the form of teeth on burnishers as they have usually been formed. heretofore. In Fig. 4-, the toothed curves of the burnisher 22 have been slightly modified so that they are involutes of a base circle slightly less that the involutes of the burnisher shown in Fig. 3; thisis indicated by the line 0 being slightly less than the line 6.

In these Figures 3 and 4.- the dimensions indicated by the lines a, b and c are the normal distances between parallel planes in contact with corresponding sides of adjacent tooth curves. These dimensions also correspond exactly with the normal pitches re spectively of the gear and burnishers. This dimension, that is, the normal pitch of the gear and burnisher, is preferably measured substantially in the manner indicated as by obtaining the distance between parallel planes provided on members of a measuring instrument when these are held in contact with adjacent teeth of a gear.

The teeth therefore of the burnisher in Fig. 4 in their intermeshing relation with the gear A being burnished will have their contact concentrated upon the points of the teeth, the greatest pressure being exerted at the extreme points and this ressure being gradually diminished until tl ie pitch circle is reached. The flanks of the teeth or portions within the pitch circle are not acted upon at all by this burnisher having a shortened normal pitch. On the either hand,

burnished in such a way. that they the burnisher shown in Fig. i whichhas a normal pitch exactly corres onding to the teeth of the gear A being urnished, will have a burnishing action uniformly distrib-. uted. over the entire involute surface of the gear tooth.

In Fig. 5 three burnishers disposed in the same way as burnishers 22, 23 and 24 are shown, each having a slightly different nor- 'mal pitch., In this figure 1) indicates the normal pitchof the gear being burnished. The burnishers 22, 23 and 24 have, as indicated, normal pitches a, b and a respectively less than, equal to, and greater than the normal pitch of the gear.

It will be seenfrom the above that I have provided a device for burnishing gears which will enable a gear to be quickly mounted in position to burnished and which may be simultaneously actedupon by a pluthree being rality of burnishers preferably used as shown in thedrawing. 'By making use of three burners 22, 23 and 24'so that they may engage the gear being burnished upon three approximately equally spaced points, I am enabled to dis ense with mounting the gear being burnis ed on centers or upon an arbor. To mount the gear such as shown at A, it is only necessary to place it in position to rest upon the burnishers 22 and 23 and then elevate the knee 11 until the gear A contacts with the rotating burnisher 24:. The burnishers 22 and 23 may then be forced vertically-upward until the gear A is forced into contact with all three burnishers.

What I claim is:

1. The process of burnishing gears comprising running said gear while in mesh with a burnisher, said gear and burnisher being of slightly difierent' normal pitch.

2. The process of burnishing gears com prising running-a gear while in mesh with a burnisher, the normal pitch of the burnisher being slightly less than that of the gear being burnished.

3. The process of burnishing gears comprising running a gear whilein mesh with a pluralityv of burnishers, one of said burnishers havinga normal pitch slightly different from that of the gear being bur- I'llShGCl. I:

4. The process of burnishing gears comprising running said gears while in mesh with a plurality of burnishers, one of said burnishers having a, normal pitch corre- .bemg burnished, the other burnishers havimg different normal pitches, the normal pitches of the latter burn-ishers being slightly less than the normal pitch of the gear.

6. The process of burnishing gears comprising running a gear while forced into contact with a plurality of approximately equally spaced burnishers whereby said gear may be retained in position by its engagement with said burmshers.

7 The process of burnishing gears comprising running a gear while forced into contact with, a plurality of burnishers mounted so as to be movable toward or from each other and adapted when in position to retain the gear being burnished between them.

8. The process of burnishing gears comprising runningl a gear while forced into contact with t ree approximately equally spaced burnishers,two-of said burnisher's being movable toward or from the other, and rotating all of said burnishers and gear from one of said. burnishers while said burnishers and gear are in mesh with each other.

In testimony whereof, I hereto aflix my signature.

1 BRYANT H. BLOOD. 

